The present trend is to replace systematically, for ecological reasons, the halogenated propellent gases of the "Freon" type in aerosol containers for hair, but the replacement of such propellants with less harmful gases such as dimethyl ether (DME) requires a far-reaching modification of the formulations. In fact, such a replacement affects not only the ratios of the various ingredients but also the very nature of the latter, and very particularly that of the film-forming substances.
It is well known, in fact, that an aerosol lacquer for setting hair must satisfy a certain number of criteria and, among these, a good ability to lacquer the hair even in an atmosphere with a high moisture content without an effect of stickiness of the hair being observed.
It is moreover appropriate that the hair should have a natural appearance, the hair being shiny and soft and that it can be combed without producing a powdery effect.
Furthermore, the viscosity of the compositions to be sprayed must be such that it can allow a good distribution by means of the valve device.
The use, in hair-care compositions and aerosol lacquers propelled by halogenated hydrocarbons, of polymers resulting from the polymerization of sulphonic acid derivatives optionally with other monomers such as alkyl acrylate derivatives or acrylamide derivatives has been described in French Patent No. 73.27329.
This French patent, the subject of which is particularly general, does not however describe or suggest aerosol lacquers in which the carrier is water and the propellant dimethyl ether.
The use of dimethyl ether as a propellent agent for water lacquers raises, in fact, many difficulties relating to the solubility and homogeneity of the compositions.
After various investigations into many copolymers containing units derived from the polymerization of unsaturated sulphonic acids it has unexpectedly and surprisingly been found that, in order to obtain aerosol lacquers which have good cosmetic properties and a good lacquering capacity at the same time, a very strict choice is necessary, not only concerning the nature of the copolymer but also that of the neutralizing agent and of the degree of neutralization of the sulphonic acid functional groups of the copolymer.
Such a choice has made it possible, in fact to reveal an excellent solubility in water of the copolymers in combination with a good compatibility with dimethyl ether.
Furthermore, it has been found that the copolymers of the aerosol lacquers according to the invention also have to meet a very precise criterion of viscosity with a view to obtaining aerosol lacquers exhibiting good distribution.